JEE Main · 2023 · Shift-IIhardHC-038

The major product for the following reaction is:

Hydrocarbons · Class 11 · JEE Main Previous Year Question

Question

The major product for the following reaction is: image

Options
  1. a

    Option A

    ✓
  2. b

    Option B

  3. c

    Optionn C

  4. d

    Option D

Correct Answera

Option A

Detailed Solution

Step 1: Identify the starting material and reaction

The reaction involves acrylonitrile (CHX2=CH−CN\ce{CH2=CH-CN}) undergoing nucleophilic addition. The nucleophile is HOCHX2CHX2SH\ce{HOCH2CH2SH} (2-mercaptoethanol) or a similar thiol/alcohol.

Step 2: Determine nucleophile selectivity

In Michael addition to CHX2=CH−CN\ce{CH2=CH-CN}:

  • Both −SH\ce{-SH} (thiol) and −OH\ce{-OH} (alcohol) are potential nucleophiles
  • Sulfur is a better nucleophile than oxygen in Michael additions (softer nucleophile, better for soft electrophile like β\beta-carbon of CN\ce{CN})
  • The thiol (−SH\ce{-SH}) reacts preferentially

image Answer: Option (a)

Key Points to Remember:

  • Michael addition: nucleophile adds to β\beta-carbon of α,β\alpha,\beta-unsaturated system
  • −SH\ce{-SH} > −OH\ce{-OH} in nucleophilicity for soft electrophiles (HSAB principle)
  • −CN\ce{-CN} group activates the β\beta-carbon for nucleophilic attack

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